Stop-on-signal radio receiver



April 10, 1956 w. J. O'BRIEN STOPONSIGNAL RADIO RECEIVER 3 Sheets-Sheet 1 Original Filed April 10, 1941 w 7 i Z W R a i a l J: Q i W o P M wfl o 5 a i J x o J 6 o 7% Q ,M u 5 W a m il a z w F 9 4. 5 9 w 4 m v f ...l l l i i. l Z 0 3 we W W ATTORNEY W. J. O'BRIEN STOP-ON-SIGNAL RADIO RECEIVER 9 1 Q 1 "m P 15 Sheets-Sheet 2 Original Filed April 10, 1941 :THE1

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STOP-ON-SIGNAL RADIO RECEIVER Original Filed April 10, 1941 3 Sheet eeJL 3 Jim -I INVEN BY fag zvs y United States PatentO STOP-ON-SIGNAL RADIO RECEIVER William J. OBrien, London, England, assignor, by mesne assignments, to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application June 12, 1947, Serial No. 754,194, which is a division of application Serial No. 387,908, April 10, 1941, now Patent No. 2,442,430, dated June 1, 1948. Divided and this application November 24, 1952, Serial No. 329,850

9 Claims. (Cl. 250-20) The present invention relates to improvements in stopon-signal radio receivers and control circuits therefor including fast-operating, low impedance relays, and more particularly to circuits wherein said relays are controlled by means of gas tubes and is a division of Serial No. 754,194, filed June 12, 1947, now Patent No. 2,620,460, issued December 2, 1952, in turn a division of Serial No. 387,908, filed April 10, 1941, now Patent No. 2,442,- 430, issued June 1, 1948.

The present invention relates also to the provision of new and improved stop-on-signal radio receiver circuit arrangements for preventing deleterious efiects resulting from oscillations in circuits including gas tubes, fastoperating, low impedance relays, and condensers utilized to provide the relays with current impulses to increase the rapidity of operation thereof.

This invention relates also to the provision of new and improved gas tubes, and more specifically to the provision of gas tubes having an auxiliary anode by means of which the gas in the tube is maintained ionized and the tube conductive in spite of fluctuations in anode potential to values below that at which the gas would be deionized and the tube rendered nonconductive.

The present invention further relates to the provision of a new and improved stop-on-signal or stop-on-carrier control for radio receivers, certain forms of which are disclosed and claimed in the copending applications of Edward F. Andrews, Serial Nos. 219,713, now Patent No. 2,262,218, issued November 11, 1941; and 275,437, now Patent No. 2,326,737, issued August 17, 1943, and my copending applications, Serial Nos. 387,907, now Patent No. 2,426,580, issued August 26, 1947; 681,183, now Patent No. 2,526,266, issued October 17, 1950, and 683,312, new Patent No. 2,249,712, issued November 29, 1949.

The present invention relates especially to the use of the special type of gas tube with an auxiliary anode in a stop-on-carrier control system of the type shown in my above-mentioned copending application, whereby the number of tubes required is reduced by one.

Other aspects and advantages of the present invention will become apparent from the ensuing description, in the course of which reference is had to the accompanying drawings, in which:

Fig. 1 is a diagrammatic representation of a control circuit for a fast operating relay embodying the present invention;

Fig. 2 is a side elevational view, partly broken away, of a gas tube constructed in accordance with the present invention.

Fig. 3 is a fragmentary vertical cross sectional view taken along the line 33 of Fig. 2;

Fig. 4 is a View similar to Fig. 3 of another embodiment of the tube;

Fig. 5 is a fragmentary perspective view of a further embodiment of a tube constructed in accordance with the invention;

Figure 6 is a diagrammatic representation of a standard 2 automobile superheterodyne receiver, in connection with which the present invention has been utilized; and I Fig. 7 is a diagram showing the details of a portion of the circuit of Fig. 6.

The circuit arrangement illustrated in Fig. 1 comprises a relay 10 whose energization is controlled by a gas tube 11. In order to effect fast operation of the relay, it is constructed to have a low impedance and low inductance winding so that with a given voltage a large current flow through it will be established in a short length of time. The low impedance and inductance are obtained by utilizing low resistance wire and winding having relatively few turns. Reduction of the number of turns reduces the actuating force exerted by the relay as the number of ampere turns is reduced (assuming the voltage supplied to the relay to remain the same), and to compensate for this reduction and to obtain fast operation the relay winding, indicated by reference character 12, is supplied with a considerable current impulse upon energization by means of a condenser 13 discharging through the winding when tube 11 is rendered conductive, the discharge flowing through the tube. This discharge of a large current by the condenser occurs rapidly because of the low impedance of the relay winding and of the gas tube, thereby to efiect fast operation of the relay. However, the circuit including the relay winding, tube and condenser has a tendency to oscillate because of its low resistance, and the oscillations reduce the anode potential of the tube and are likely to cause deionization of the gas in the tube and to render the tube nonconductive. These fluctuations are prevented from deionizing the gas in accordance with the present invention, as illustrated in Fig. l, by providing the tube with an auxiliary anode supplied with a potential suflicient to maintain ionization of the gas in spite of fluctuations in anode potential.

In addition to the auxiliary anode, indicated by reference character 14, the tube is provided with an anode 15, a grid 16, an indirectly heated cathode 17, and a cathode heater 18. The physical construction of the tube may take various forms, three forms being shown in Figs. 2 and 3, 4, and 5. In the embodiment of Figs. 2 and 3 the tube is shown with the usual glass envelope 19 and base 20. The envelope surrounds the previously enumerated elements of the tube and contains an ionizable gas. The anode 15 is cylindrical in shape and is supported in conventional manner by a pair of spaced posts 21 between insulating plates 22. The cathode 17 is cylindrical in shape and supported concentrically with respect to the anode by a refractory post 23 in which the cathode heater 18 is embedded. The grid 16 is a helical wire located in proximity to the cathode and concentrically arranged with respect to both the cathode and anode. The auxiliary anode 14 is also a helical wire, it being located in this embodiment in proximity to the anode and concentric with respect to the other tube elements. Suitable leads are brought from the tube elements to prongs on the tube base 20. All the tube elements are of substantially the same length in order that the tube may operate in its intended manner, as will be described shortly in connection with Fig. 1. v

The tube illustrated in Fig. 4 is similar to that just described except that the grid and auxiliary electrode are constituted by metallic cylindrical members 24 and 25 provided with two or more aligned apertures 26 and 27, respectively.

The tube illustrated in Fig. 5 differs from those previously described mainly in that the grid and auxiliary anode are constituted by apertured flat structural ele ments 230 and 231, respectively, and the anode by a cylindrical wire 232. These elements and the cathode 233 and cathode heater 234 are surrounded by a grounded metallic shield 235, the open ends of which are closed by n i g P es 23 The hi ld emrrisss as s um partition 237 located between the grid and auxiliary anode, thus defining two compartments, one for the cathode, cathode. heater and grid and a se nd for the. auxiliary anode and anode. The apertures in the grid, partition and auxiliary anode are in alignment with each other and the cathode and anode. A tube of this construction may be constructed simply and economically and possesses a high control factor.

Returning now to a further detailed description of the circuit of Fig. 1, it may be seen that the relay winding 12 is composed of two series connected coils, One terminal of the winding is connected directly to anode. 15 by conductor 28 and the o her to the positive terminals of a source of potential, such as battery 30, through a current limiting resistor 31 and conductors 32 and 33. The battery thus serves as a source of anode potential for the tube and as a source of energizing current for the. relay. The other t rminal of th attery i ounded. h ou h conductor 34.

The p wer cons mption of. the r lay is redu d by th resi t r. 3 whi h s chosen to h e a a ussuch that once the relay is ner ized, the urr n fl w herethrc is only u nt t main ain th r lay i p ated pos tion.

Th current pulse s pplyi g con enser 1.3 is c n nected to the cathode by conductor 35 and to a point inten mediate the relay and resistor 31 by a @Onductor 36. It is thus connected so as to be charged by battery 30 when the tube is nonconductive and to discharge through the tube and relay when the tube is conductive.

The auxiliary anode is supplied with ,a potential sufii cient to maintain the gas ionized and the tube conductive in spite of fluctuations in anode potential from a suitable source, preferably the battery 30, through a current limiting resistor 37 and conductors 38, 39 and 33.

Grid-bias voltage is obtained through the use of an ad.- justable resistor 40 connected between the cathode and ground. This resistor is connected to the cathode by conductor 41 and to ground through switch 42 and ground connection 43. The grid is connected to. ground through conductor 44, resistor 45 and conductor .46. A grid-bias voltage sufiicient normally to maintain the tube nonconv ductive is obtained by connecting the cathode end of bias resistor 40 to the battery through a bleeder resistor 47.

The tube is rendered conductive by rendering the grid more positive and this .can be accomplished as by applying a positive signal voltage across the terminals of Iesistor 45 by means of conductors 48.

The relay may be utilized to control circuits or mechanisms and the like. in stop=on-carrier controls it is utilized to control vci-rcuitsand a clutch, as indicated in Fig. 1. shown in Fig. 1 being of a novel construction requiring but little space. It comprises a metallic base 49 having an upturned flange 50 at its front end. The coils 12 together with their cores 51 are secured to the flange. The cores have upturned ends above which is supported an armature 52 mounted at the ends of contact carrying switch blades 53 and 54. The switch blades are biased upwardly normally to complete circuits through fixed switch blades 55 and 56 and are movable downwardly upon energization of the relay to complete circuits throngh switch blades 57 and 58, respectively. The switch blades as well as the terminals to which conductors 28 and 32 are attached are mounted at the rear of base 49 by spacer blocks 59 and suitable bolts. The spacer blocks are made of insulating material to insulate the terminals and switch blades from one another.

Switch blades 53 and .54 are biased upwardly by ,a spring 60 that serves also to maintain the clutch engaged whenever the relay is deenergized. The biasing isefiected through a combined clutch operating and power transmitting rod 61 slidably and rotatably .rnountedin a supporting bearing 62 forming part of the base member. The spring 4 is held between the bracket and a washer 63 secured to the rod above the bracket. 7

The clutch comprises a pair of selectively engageable elements 64 and 65, the former of which is secured to rod 61 and the latter of which is driven from a suitable source of motive power, such as an electric motor, by gear 66. When the clutch is engaged, as indicated, a rod 61 is roated o. impart m em nt a dr n. ear 1 used o d i tu in co den e s in stop en csrr t eat e s as will be explained more fully in connection with Figs. o and 7.

In the description of the operation it is assumed that he tu is nencqu eti e by reasen ofthe s ap li to 7 rid 16 nd tha as a r sult relay 1 is de ner 'ed- At The relay may also take various forms, that a this i e h id s biase n at ve b r as of u rent flow through resistors 40 and 47, which are connected across the battery 30 through conductors 33 and 39, switch 42 and ground connections 34 and 43. The condenser 13 is fully charged by reason of its connection to the battery and battery potentials are applied to auxiliary anode 14 and anode 15.'

The tube is rendered conductive and the gas therein ionized when a positive signal of suflicient strength is applied across resistor 45, after which the grid 16 becomes inefiective to exert further control. Immediately the tube is rendered conductive, current flows through the relay windings 12 and fast operation of the relay'is insured by reason of its low resistance and impedance and the discharge of condenser 13 therethrough. The low resistance series circuit including the condenser, tube and relay winding has a tendency to oscillate with the result thatthe potential applied to anode 15 may be periodically reduced to a value below the potential required to maintain ionization. In the ordinary three element gas tube the result would be the deionization of the tube, but in the described apparatus, the gas in the tube is maintained ionized by the auxiliary anode 14, which is connected to the battery through resistor 37 and which is not affected by the oscillatory circuit.

' The relay is supplied with current suificient to maintain it energized through a circuit including the battery, ground connections 34 and 43, the tube and resistor 31. Resistor 31 is so proportioned that it limits the relay current to the desired value, Resistor 37 is so proportioned that only a very limited amount of current flows through it, thereby reducing power consumption by preventing any substantial flow o f current through it and the auxiliary anode excess of that required to maintain ionization When it is desired to deenergige the relay and to render he ube o co du t e, it s necessary n y o nt r l t pen s tc 42- Openin of t switch resu ts in the opening of bo h t e mend au iliar nod r ui as the switch is in series with the tube and battery.

The Pre ent n n ion is Part ula l ad tedfe st po ce erre b re ei r so g-0. T e se'n a as ub p vided th n a x a an de resu ts is a reduc i n '01 the n m er o t be re ired or insta ce hen used in a n r l o the pe d clos d n m c p ndius pp ca n one t b s e im ated All appl a n o t tu to. t is y e 9f con l s il s rated in i s 6 and 7 Reiem mo e Par cula l t F t may b noted that this figureillustrates in bloek diagram form a stand r a tomobi e su s heterpdyue re e e t wh the, elemen s o h presen nvent on ha been added- For the most part the receiver and control circuits are those is lose and c aimed i .t y Pa en s o 2 6 58 2,526,2 6 and 12 8 12 pr vi usly .nienti ned, and onsequently only the portion of the circuit associated with the operation f the ovel s tube otthe p es n in tion will be described detail hereinafter.

Th r ceive com ri es a aeria 1. a r d e uen y stage 111, a first detector and oscillator section 112, an interm di te i r-a eusy sta e L3, a secon t r's ion .14, a ba a ce bridge cir u t s t n 1. .5 form part of the stop-on-carrier control and illustrated in greater sietai in Fig. 6, gas tube 116 al o crnsinsne q tlles g eg'iagnper 15 on-carrier control, a volume control potentiometer-117,,an audio frequency amplifier section 118, and a loudspeaker 119.

Energy is supplied by a battery 120 adapted to be connected by a switch 121 to a tuning means operating motor 122 of the reversible type, a cathode heater circuit 123, r

and through an interrupter, step uptransformer and "B" supply unit 124 to a B supply line 125. The B supply line leads to the various receiver portions and thestop-oncarrier control in a manner to be considered in great detail hereinafter. The switch-121 is illustrated as a manually operable switch, but it may be operated by the motor 122, as set forth in my copending application.

The receiver is provided with the usual tuning condensers 126 which are actuated by motor 122. The timing and receiver volume are controlled from a remote point, such as the dashboard of an automobile, by means of a tuning control switch 127, which is normally closed, and a volume control switch 128, which is selectively operable from a normal circuit breaking position into which it is biased as by springs) to the left to increase the volume and to the right to decrease the volume. I

Before describing indetail -thc various control means and control circuits, it may. be well to review briefly the mode of operation of stop-on carrier radio receiver control. In so far as tuning is concerned, the tuning is initiated manually at the remote point by momentary opening of switch 127. This sets the motor in operation to rotate the tuning condensers through a clutch until the-receiver is tunedto the carrier frequency of a station received with a certai'n intensityff .jlhemotor operates firstin one direc-,

tiono ver the en ire range "of movement of the condensers and thenjn the other, the"' irect ion of rotation of the motor beingcon'trolled'hy'limit switches cooperatively associated with ,the condenser I'Ihe ,same motor is usedg't'o control{thevolunie'but,.'yvhen"so used, it is selectivelyoperable in either e t ii pon operation of switch 128 to either' of-itsftwopositions; "'Ihevolume control also includes a"clutch through which themo'tor is selectively connected to the'rnovable portion of the potentiometer 117 heretofore referred to.

. Referring again to Fig. 6, it may be noted the condensers 126 are mounted for rotation with a shaft 130 connected by gears 131 toa shaft 132. The latter is adapted to be connected to a shaft l33driven by motor 122 whenever a relay 134, associated with the stop-.onfcarrier control, is deenergized or released, at which tinie'the clutch 135 is engaged. The relay and clutch may be constructed in accordance with those illustrated in Fig. l, i. e., the relay is of the: fast acting type'and the clutch is operable by the relay armature. The energization of the relay is controlled by gas tube 116 and when it is energized, shafts 132 and 133 are disconnected to prevent further driving of the; condensers whenever a station received with a certain intensity is tuned in. As already indicated, the tuning condensers are rotated first in one direction and then the other, the direction of rotation being reversed at the limits of their movement by a limit switch 136 operated by two arms or the like 137 suitably secured to condenser shaft 130. p v

The volume control includes a clutch 138 operable by a relay 139 and adapted whenever the relay is, energized to interconnect shafts 133 and 140. The latter is operatively connected to the movable member of potentiometer 117.

The motor 122 has a pair of windings 141 and 142 selectively energizable to rotate the motor in opposite directions. Winding 141 is connected by conductors 143 to the right contact of volume control switch 128 and by branch conductor 144 to one of the two contacts associated with limit switch 136. Winding 142 is connected by conductor 145 to the left contact of the volumecontrol switch and by a branch conductor 146 to the other contact of the limit switch. 'Themovable blade of volume controlswitch 128 is c'onnected by conductor 147 to one terminal of clutch operating relay 139, the other terminal of whichis grounded. Thus, when switch 128 is operated to either of its two positions, the motor is energized simultaneously with energization of the relay and, as a result, the movable member of the potentiometer is operated in one direction or the other to increase or decrease the volume of reception. The energizing circuit is completed in both cases through the armature of motor 122, switch 121, battery and ground.

The remote tuning control switch 127, which is opened to initiate the tuning of another station, has one of its fixed contacts connected to conductor 147, this conductor serving, as will appear more fully hereinafter, as a ground connection, and its other fixed contact connected to adjustable resistor 148. A conductor 149 connects the lat ter to the cathode of gas tube 116 whereby the switch and resistor are included in the plate circuit of the stopon-carrier gas tube 116.

The energization of motor 122 during tuning is controlled by relay 134 which actuatcs switch blades 150 and 151. Switch blade 150 has associated with it a pair of relatively fixed switch blades 152 and 153, while blade 151 has associated with it a relatively fixed blade 154. Blades 150 and 151 are connected to ground by conductor 155. Blade 152 is connected to limit switch 136. Blade 153 is connected by conductor 156 and an AVC delay condenser 157 to an AVC conductor 158. Blade 154 is connected by conductor 159 to the grids of the tubes of the last stage of audio amplification.

Thus, when relay 134 is deenergized, as it is during the actual tuning operation, the condensers 126 are connected to the motor shaft through clutch and one or the other of the two motor windings is energized, the energizing circuit"extending from the battery, through the motor armature, one'or the other of windings 141 or 142 depending upon the position of limit switch 136, switch blades 152 and 151, and ground connection 155 back to the battery. At the same time conductor 156 and condenser 157 are disconnected from ground to provide fast acting AVC, while conductor 159 is connected to ground through switch blades 151 and 154 and conductor 155. Connection of conductor 159 to ground serves to connect the grids of the amplifier tubes of the last amplifier (audio frequency) to ground to mute the loudspeaker during tuning. When the relay is energized by tube 116 becoming conductive, as now about to be described, the condensers are declutched from the motor and the latter de energized. The motor is deenergized by reason of the opening of its energizing circuit by disengagement of blades and 152. The AVC delay condenser 157 is simultaneously rendered effective to increase the time delay applied to the AVC'voltage to a value necessary for proper reception during normal reception. Furthermore, the ground is removed from the audio-frequency amplifier tubes to condition these for normal operation.

The primary function of gas tube 116 is to control the energization of relay 134 so that it is substantially instantaneously operated when the receiver is tuned to the carried frequency of a broadcast station. A further func tion of this gas tube, which is provided with an auxiliary anode 17.7, is to employ the high positive control voltage impressed on the auxiliary anode to prevent premature deionization of the tube as a result of oscillations in the plate circuit after it has been ionized. To fulfill this func tion, the gas tube 116 operates in a manner somewhat similar to that described in connection with Fig. 1. The relay is energized when the tube is rendered conductive and the latter is rendered conductive whenever the condensers 126 are rotated to tune the receiver to the carrier frequency of a broadcast station. To insure the tube be ing rendered conductive when the station is exactly tuned in, the tube is controlled in response to the tuning. In brief, the tube 116 is controlled by two potentials, one acting upon the auxiliary anode 177 and the other upon a grid 212 These potentials vary with the tuning of the 7 e r and ea e 9 tu s sen q i s hen. e an ics is substantially exactly tuned; to a frequency.

Referring n m r tic larl o Fi hi ffis uq' illustrates in greater detailcertain portions of the'apparatus, illustrated diagrammatically inl ig. 6. These portions are those from which the control potentials for d e gas tube are obtained. Corresponding elements of Figs. '6 and 7 are indicated by like referenc'characters.

The radio frequency section 111 of Fig. 6 is shown to comprise a tube 171. Its control grid is coupled in conventional manner to the antenna by conductor 17?. and connected to the AVG conductor 158 through resistor 173. Its anode is connected to the primary winding 1 7 4 of a coupling transformer which has not been illustrated in full but which is utilized to connect tube 171 to the first detector and oscillator section 112, which likewise has not been illustrated in Fig. 7. The terminal of winding 174 remote from the anode is connected to the 8" supply conductor'125 through conductor 175. and resistor 176 and to the auxiliary anode 177 of the gas tube through conductor 175. and a resistor 178; The same terminal is also. by-passed to ground through condenser 177A.

The automatic volume control includes a resistor 179 connected between conductor 158 and a conductor 180 leading to a source of AVG voltage to be referred to later. It also includes a very small radio frequency ,by-pass condenser 181 connected between conductor 158 and ground and the previously mentioned AVC time delay condenser 157 that is controlled by switch blades 150 and 153 oper ated by relay 1,34.

The output from the radio-frequency section 111 is, as already described, supplied to thefirst detector and oscillater section 112 and thence to the intermediate frequency section 113 A portion of the output from the latter is supplied to the second detector stage 114 and a portion to the balanced bridge circuit and stop-oncarrier control section 115.

The intermediate frequency section comprises a tube 182, the anode of which is connected to one terminal of the primary winding 183 of a closely coupled transformer, the other terminal of which is connected to B supply conductor 125. A portion of the output of tube 182 is supplied to the detector stage through the secondary winding 184,0i the transformer. One terminal of winding 184 is connected to the detector anode 1-85 of a multi-function tube 186 through conductor 187; and the other terminal by conductor 188 to volume control resistor 117, which is shunted by condenser 189 and together with the detector diode section of tube 186 serves also as the source of AVG voltage. The other terminal of resistor- 117 is connected to the cathode 190 of tube 186 by a grounded conductor 191.

Tube 186 also serves as the first stage of audio-frequency amplification. Its control grid 192 is connected to the movable member of the volume control potentiometer through a suitable source of grid biasing potential, such as battery 193, conductor 194 and condenser 195. The grid is further connected to ground by a grid leak resistor 196. The amplified audio-frequency output is supplied to the succeeding stage of amplification through the. anode connection 197. From the foregoing description it may be noted that the-circuit of Fig. 7 does not correspondenactly to the block diagram of Fig. 6, in that in the latter the second detector and audio-frequency. amplifier sections have been entirely separated. However, in a practical installation the tube 186 may well perform the dual function of a detector and amplifier, and it has been illustrated as doing this in Fig. 7. As a matter of fact, and as will appear shortly, tube 186 is utilized also as a rectifier to provideasecond control potential for gas tube 116.

The second. ont potenti l e a ube 1.1.6. s ob: tained by means ofa balanced bri gi ircuit 20p.so,con-. structedand arranged that it is critically responsive-to he on. at a sta n descri ed n my aten s, Nos. 2,42 .580 and 2,489,712; This circuit eon: ri s cs a rst a k. c rc i ncluding pr mar nding 11 co en e con ense 2%, r s t 2 3.. nd an dju tae onden e 4 whereb i c i m y be ed o re ce he inte media r que iq T ei it a ww r ses. a se nk. rcui c u fns on en e inductance coil 2G5 and an adjustable condenser 206' for tuning this tanlc circuit to resonance at the intermediate frequency. The common connection of condensers 201, It. and 206. is grounded; The common side of winding 183 and condenser 204 is connected to the common side of inductance 205 and condenser 206 through condenser 207.

The "output from the bridge circuit is led to the anode 208 of the second diode rectifier section of tube 186 through a condenser 209' and conductor 210, and the rectified outpu app a ng as avoltage drop across resistor 2. is p i 9 e on r add. 2. 2 o a b r u h ime. delay. c r t n ludin h s or 1 and condenser 213. The resistor 212" is in series with the ri ea qnnjq ns h rid. 2 he. a od an of s'istor 211 A radio frequency by-pass condenser 215 is connected across ground conductor 191 and the previously referred to conductor: 149 leading to the cathode 216 of gas tube 116.

The relay 134 is connected to anode 218. of tube 116 by conductor 21? and the 8" supply is connected to the anode through the relay winding and current limiting resistor 2 20. A current impulse is supplied to the relay winding when the tube is rcndet ed conductive by a condenser 221 having one terminal connected to the cathode 216 through conductor 149 and its other terminal con; nected to point intermediate relay winding 134 and resistor 220. A bleeder resistance 222, connected at one a n th .3" surp y an t e h en to he cathode lead 149, provides proper bias of the grid 212, when the tube is nonconductive, current flowing therethrough and the pr evjously mentioned bias adjusting resistor 148.

The operation of the system of Figs. 6 and. 7 is as tollows:

The receiver is put into operation by closure of switch 121 which completes an energizing. circuit for motor 122 extending from the battery 120, switch 121, the armature of motor 122 winding 142, conductors 145, 146,, limit switch 136 switch blades 152, 150, and back to the battcry through ground connection 155. Since clutch is engaged when relay 134 is deenergized, as it is at this time, the motor: rotates the condensers 126 first in one direction then the other as the windings 141 and. 142 are alternately energized by operation of limit switch rom nern i pn 9. ma hs: y thea s mou e on condenser shaft 130.-

rotation of the condensers. in alternate directions continues,- untilthe various tubes;

- are heated and a. broadcast station received. When a station is received, the gas tube 116.is rendered conductive and relay 134 immediately operated to declutch the condensers. from the motor shaft and todeenet'gize the motor.

The gas tube is rendered conductive by the application. of an. increased positiye potential on the auxiliary anode 177 andby. a redu tion of the negatisle voltage impressed on the grid 212, from the.,dicde 208. The auxiliary anode rs made more positive as aresult of the application of automatic volume control voltage to the grid of'radiov frequency tube 171 This controlvoltageis obtained from the second. detector section of tube. 186 and is applied to the grid of: tube 171 througha circuit includingconductor 180, resistor 179, conductor 158, resistor 173, and conductor 17.2. Asa result of the application of. his controlvoltage-on thegrirl of tube 171, the plate current of this tube is decreaeer'l, with the further result that the vqltage. drag. act ss esis o 1 i de r as d and. n. n eased QQSifiEQBQIGQfiQL 4l2it d1 he. x ia y anode 1 wh sht s onnected o anode d ti so e- Z This connection is through resistor 178 which serves to limit current flow through the auxiliary anode. The voltage applied to the auxiliary anode rises rapidly as a station is being tuned in and is at a maximum when a stat on 18 exactly tuned in, as described at considerable length in my Patents Nos. 2,526,580 and 2,489,712.

The voltage thus applied to the auxiliary anode 177 when ionization occurs is considerably in excess of the ionizing potential, and remains so until the next station is tuned in by manually operating push button switch 127, to deionize tube 116. Thus, even though oscillation in the circuit, including tube 116, relay 134, and condenser 221, may reduce the voltage of the plate 218 below ionizing potential, ionization is maintained regardless o f the potential on the plate by the potential on the auxiliary anode 177, which remains continuously above the ionizing potential until the switch 127 is again opened.

The balanced bridge circuit 200 supplies a signal to the diode 2438 which increases as resonance with the sta tion is approached until it is within about one kilocycle of resonance. From this point the amplitude of this signal falls rapidly, substantially to zero. Thus, a negative direct current voltage from the diode 298 is applied to the grid 212 of the gas tube 116, which increases as resonance is approached to a maximum negative value around one kilocycle from resonance, and then falls steeply substantially to zero at resonance. The reduction of this negative signal on the grid 212 when the station is correctly tuned in, together with the previously described increase in the positive voltage applied to the auxiliary anode 177, effects ionization of the tube 116 and stopping of the condensers 126 at a position correctly to tune in the station.

The primary winding 183 of the transformer associated with the intermediate frequency tube 182, condenser 204, resistance 203, condenser 292, and the mutual reactance of condenser 297 constitute a tank circuit tuned to the intermediate frequency. Condenser 202, inductance 205, condenser 206, together with the mutual reactance of condenser 207, also constitute a tank circuit tuned to the intermediate frequency. This circuit is excited through condensers 2G2 and 2437. The coupling of these tank circuits through condenser 292 is inversely proportional to the frequency, while the coupling through condenser 267 energizing the inductance 295 is proportional to the frequency. Due to these opposing couplings and the parameters of the elements of the two tank circuits, the potential appearing across condenser 206 is substantially zero when a signal of exactly intermediate frequency is placed across the primary winding 183. In other words, the effect of the coupling occurring through condenser 207 produces a voltage drop across the inductance 205 which is equal and opposite to the voltage drop across condenser 262 at resonance. The value of resistance 203 is selected so as to bring the voltage across the condenser 292, 180 out of phase with the voltage across inductance 205. Under these conditions there is substantially zero voltage across condenser 206 at resonance. In one aspect the arrangement of the coupled circuits may be considered as a balanced bridge circuit or a circuit providing zero coupling at resonance.

n the other hand, if the signal across the primary winding 183 is slightly out of resonance, there is no longer a balance between the opposing couplingsthat is, the efiect of one coupling is greater than that of the other, and a potential varying with the departure from resonant frequency exists across condenser 206. When the condensers 126 are approaching exact tuning, that is, one or two kilocycles away from exact tuning, a very large alternating current voltage is applied to the anode 268 of the rectifier section. The output of the rectifier appears as a voltage drop across resistor 21} and this voltage is applied through resistor 212 to the grid 212 of tube 116. The greater the voltage applied to the anode 298 of the rectifier, the more negative the grid 212.

The normal negative bias of the grid 212 due to the biasing resistor 148 and the bleeder resistance 222 is such as to render the tube conductive when the negative bias applied to the grid 212 from the balanced bridge circuit and rectifier approaches a minimum value (which occurs at resonance) so that when a station is exactly tuned in, the tube is rendered conductive by the conjoint actions of the less negative grid and more positive auxiliary anode, 177. When the tube 116 is ionized, the plate to cathode resistance of the tube drops to a relatively low value. The condenser 221, which accumulates a high charge through its connection to the B supply through resistor 220 during the nonconductive period of tube 216, now discharges rapidly through the low impedance winding of relay 134, with the further result that the relay is instantly operated to declutch the condensers from the motor shaft and to deenergize the motor, thus stopping the condenser exactly on the carrier frequency as previously explained. The steady flow of current through the resistor 220, relay winding and tube, which are connected in series across the B operated position once it has charge of condenser 221.

As heretofore explained, the operation of the switch of relay 134 results also in the disconnection of conductor 159 from ground, thereby removing the ground connection from the last stage of audio-frequency amplification, and the output of the receiver can be heard through loudspeaker 119. The relay also efiects connection of switch blades 159 and 153, with the result that condenser 157 is connected to ground to render it effective to increase the time delay applied to the automatic volume control voltage necessary for proper quality reception during audible reception of the signal.

Vhen it is desired to tune in a different station, switch 127 is momentarily opened, thereby effectively breaking the plate circuit of the gas tube which results in the deenergization of relay 134. The motor is thereby energized and the condensers are connected to the motor shaft. The tuning operation described above will be repeated and the motor again deenergized, and the condensers declutched upon reception of another signal exceeding a certain strength. The signal strength at which the tuning means will operate may be adjusted at will by means of the adjustable resistor 143 which serves to control the normal negative bias of the grid 21?. of the gas tube.

been operated by the dis- The volume may be adjusted at any time by moving the volume control switch 128 either to the right or left, as indicated in Fig. 6. When moved into either of its circuit-making positions, the one or the other of motor windings 141 or 142 is energized simultaneously with the energization of clutch operating solenoid 139. The energization of the solenoid results in the clutching of the volume control shaft 149 to the motor shaft 133, with the result that the movable member of the volume control potentiometer 117 is operated in the direction selected by operation of the volume control switch 128.

When it is desired to turn the receiver oti, it is necessary only to open the power switch 121 which effectively cuts off the power to the radio receiver proper and to the various controls. Although the invention has been disclosed in connection with specific details of preferred embodiments thereof, it must be understood that such details are not intended to be limitative of the invention except in so far as set forth in the accompanying claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In a radio receiver, the combination including, tuning means, controllable means for moving said tuning means connected thereto, a relay having a lower impedance and relatively few turns operable when energized to stop said tuning means, and means for energizing said relay at the carrier frequency of a broadcast stapotential, is suflicient to hold the relay in its li n, s id. las mentioned m ans including a gas t b ha ng n ano and. a cathode, a ourc of. ire t current connected across said anode and cathode through a circuit including said relay and a current limiting resister, a condenser connected to said cathode. and relay operable to supply said relay with a current impulse when said tube is ionized, said condenser, tube and relay forming an oscillatory circuit, means associated with said receiver for ionizing said tube at the carrier frequency of a broadcast station, means for preventing deionization or; said tube by oscillations in said oscillatory circuit in-. cluding an auxiliary electrode in said tube and means to apply a'control voltage to said auxiliary electrode, and manually operable means for deionizing said tube.

2-. In a radio receiver, the combination including, tuning means, controllable means for moving said tuning means connected thereto, a relay having a low impedance and relatively few turns operable when energized to stop said tuning means, and means for energizing said relay at the carrier frequency of a broadcast station, said last mentioned means including a gas tube having an anode, cathode, grid and auxiliary anode, said grid and auxiliary anode being spaced apart and located in proximity to said cathode and anode, a

source of direct current connected across said anode. and cathode through a circuit including said relay and a current limiting resistor, a condenser connected to said cathode and relay operable to supply said relay with a current impulse when said tube is ionized, said condenser, tube and relay forming an oscillatory circuit, means for applying a negative ionization restraining potential to said grid, means for applying a positive potential upon said auxiliary anode, means for substantially decreasing the bias and increasing the potential applied to said grid and anode, respectively, when the receiver is tuned to the carrier frequency of a broadcast station thereby to ionize said tube and to energize said relay.

3.311 a radio receiver, the combination including, tuning means, controllable driving means connected to the tuning means, means for stopping said tunning means at the carrier frequency of a broadcast station, said last mentioned means including a gas tube having a main anode, an auxiliary anode and grid, and means for varyiug both the auxiliary anode and grid potentials to ionize said tube in response to the tuning of a station.

' in a radio receiver having a source of automatic volume control voltage tuning means and controllable driving means for the tuning means connected thereto, the combination including an electron tube having an output circuit and a grid, resistance means in said output circuit, a connection from the source of automatic control voltage to said grid, a gas tube comprising a cathode, anode, grid and an auxiliary anode, a relay in the anode circuit ofsaid gas tube adapted to be energized for stopping said tuning means when a carrier signal is closely tuned in, a source of anode potential connected to the anode of said gas tube through said relay, means for normally biasing the grid of; said gas tube negatively to a potential sufiicient to prevent ionization of the gas in said tube, and means for supplying a positive potential to said auxiliary anode and for supplying a negative potential to the grid of said gas tube and increasing the positive potential applied to the auxiliary anode arid first increasing and then reducing the negative potential applied to the grid of said gas tube for ionizing the tube when a carrier signal is closely tuned in, said last mentioned. means including a connection from the plate end of said resistance means to the auxiliary anode of said gas tube and means coupled to the. receiver for supplying a control voltage; having a minimum; value when a carrier-signal is closely tuned in. 5,. in a. ra receiver, the combination including ad iust ble tun g. means, n r l a l d i ing, me n n-- nes ed to s uni g n indexing means op rativel connected to said driving means for stopping said tunlug means on the receipt of an incoming signal including an electron tube having a main anode, an auxiliary anode, and a grid, and means for applying control voltages to the grid and auxiliary anode which vary in the opposite sense as the tuning means approaches. the resonance of a signal.

6. in a radio receiver, the combination including adjustable tuning means, controllable driving means connected to said tuning means, indexing means operatively connected to said driving means for stopping said tuning means on the receipt of an incoming signal including an electron tube having a main anode, an auxiliary anode, and a grid, means supplying a varying negative voltage to said grid as the tuning means approaches resonance of a signal, and means to supply a positive voltage to the auxiliary anode as the tuner approaches resonance to, in combination, control the tube conductance and indexing of the tuner.

7. In a radio receiver, the combination including adjustable tuning means, controllable driving means connected to said tuning means, indexing means operatively connected to'said driving means for stopping said tuning means on the receipt of an incoming signal including an electron tube having a main anode, an auxiliary anode, and a grid, means supplying a varying negative voltage to said grid as the'tuning means approaches resonance of a signal, means to supply a positive voltage to the auxiliary anode as the tuner approaches resonance to, in combination, control the tube conductance and indexing or" the tuner, and balanced resonant circuit means in the varying negative supply means which develop. opposing voltages which cancel at substantial resonance to remove. the. negative voltage applied.

8. In a radio receiver having a high frequency amplitying means, a'source of automatic volume control and. adjustable tuning means, the combination including controllable driving means connected. to the tuning means, indexing means operatively connected to the driving means for stopping said tuning means upon receipt .of anincoming signal including an electron tube having a main anode, an auxiliary anode, and a grid, said high frequency amplifying means being connected to said automatic volume control, means connecting the high fr.equency amplifying means to the auixiliary anode of the tube to provide a positive varying voltage thereon as the tuning means approaches resonance, a pair of balanced tuned circuits connected to the high frequency amplifying means and in opposing relation, rectifier means connected to the balanced tuned circuits and to the grid to apply a varying negative voltage to said grid, the potentials. on said grid and auxiliary anode. combining to control the conductance of, the tube to cause the tube to conduct, as a signal is tuned in.

9. In a radio receiver, the combination including adiustable tuning means, controllable driving means. connected to. said tuning means, indexing means operatively connected to said driving means for stopping said tuning means on the receipt of an incoming signalincluding electronic conductance means. having a plurality of electrodes connected thereto to control the current flow there.- through, and means for applying different control volt.- ages to different electrodes which vary in the opposite sense as the tuning means approaches resonance of. a signal to operate the indexing means.

References Cited in the file of this patent UNITED STATES PATENTS 

